436 PROCEEDINGS OF THE ACADEMY OF [1892. 



and deuterocones. pi has a small and simple crown. The other 

 premolars are greatly extended antero-posteriorly and are greatly 

 compressed ; on j?luid"* the deuteroconid is represented by a ridge 

 which descends from the inner side of the apex of the protoconid, 

 which is obscurely indicated on p^ but distinct on p^. All the pre- 

 molars except the first have paraconids. 



In ProGameUi-i, of the Loup Fork, the first and second upper pre- 

 molars are small and simple, in the third an internal crescent is 

 almost completed by the extension of the anterior and posterior 

 internal ridges, which have not quite coalesced, and leave a small 

 gap opposite the apex of the protocone. P4 is of the typical rumi- 

 nant pattern and resembles that of Poebrotherium. The most pecu- 

 liar stage of premolar reduction in the cameline series is, however, 

 that displayed by the Pliocene genera, Holovieniscus and Eschafius, 

 which have lost all the premolars, except the fourth, of each series. 

 In the former genus P4 is of the ordinary pattern, composed of an 

 external crescent, the protocone, and the crescentic deuterocone, 

 ■while in Eschatius this tooth is reduced to a simple cone through 

 the suppression of the internal element. 



In the Tragulina the premolars remain very simple and tren- 

 chant, with small and sharp anterior and posterior basal cusps, 

 though P4 is of the typical ruminant pattern. The curious little 

 White River genus Leptomeryx (if I do not err in referring it to 

 this group), is remarkable for the complexity of its premolars. 

 P;; and 3 have elongated and acute protocones with trenchant mar- 

 gins and well developed conical deuterocones, and on P3 a small 

 ridge passes from the anterior edge of this element to the outer side 

 of the crown, enclosing a small valley. In Tragulns the deutero- 

 cone is the merest rudiment and it should be added that specimens 

 of Leptomeryx occur with premolars as simple as those of the 

 recent genus. The lower premolars of Leptomeryx are also more 

 complex than in Tragulns. F is very small and simple and is iso- 

 lated by a diastema both before and behind it ; the succeeding 

 teeth have acute and trenchant protoconids, to which is added on 

 J? a metaconid, and on pS and^ both para- and metaconids. On the 

 latter the deuteroconid is represented by a thin crest which runs 

 back from the apex of the protoconid parallel to its posterior mar- 

 gin and enclosing a deep valley ; an indication of the same struc- 

 ture, but not nearly so marked, is visible on p^. 



